Title

Author

Date Thesis Awarded

Document Type

Honors Thesis

Degree Name

Bachelors of Science (BS)

Department

Biology

Advisor

Patty Zwollo

Committee Member

Lizabeth Allison

Committee Member

Eric L. Bradley

Committee Member

Tun-jen Cheng

Abstract

Pax5 is the master regulator of B-cell development. Pax5 is highly conserved between invertebrate and vertebrate species and is known to be alternatively spliced. An isoform missing exon 2 appears to be species independent. This is significant because exon 2 contains the DNA binding domain and thus these isoforms have decreased DNA binding, which change their function as a transcription factor. This project aimed to determine if there are changes in the alternative splicing of Pax5 during a humoral immune response in spawning sockeye salmon (Onchorynchus nerka). Specifically, this project looked at the changes in Onchorynchus Pax5 isoforms that lack exon 2, to determine if these changes correlated with an increase in the amount of secreted IgM in such animals. Real-time PCR was performed using primers that amplified full length Pax5, the Pax5Δ2 isoform, and secreted and membrane IgM. The relative expression levels of Pax5Δ2/Pax5FL were then compared to the relative expression levels of secreted/membrane IgM. This project concluded that there is a positive correlation between the levels of secreted IgM and Pax5Δ2. This positive correlation was observed in vivo in O. mykiss in the laboratory, in vitro in LPS activated B-cells from O. mykiss, and in vivo in spawning O. nerka samples for spleen and blood. This conclusion supports the model that Pax5Δ2 is acting as a co-repressor of Pax5FL by binding to the initiation complex on the Xbp1 gene, thus changing the shape of the initiation complex and preventing Pax5FL from binding to the promoter region of the Xbp1 gene.